The present invention relates to a numerically controlled working process (hereinafter referred to as an NC working process) for working an object (hereinafter referred to as the work or workpiece) by controlling a working machine by means of a numerically controlling device (hereinafter referred to as an NC device), and, particularly, to an NC working process for machining a workpiece according to a predetermined fashion.
In a numerically controlled working machine (hereinafter referred to as an NC working machine) controlled by an NC device, the tool position with respect to the work is instructed by numerical information corresponding to the tool position, and an operation or the like is performed under the control of the NC device, so that the work is machined using calculated values or the like. By means of such an NC working machine, a work can be easily machined into a complicated shape with high accuracy, and productivity can be improved.
Generally, an NC working machine is constituted, as shown in FIG. 1, by an NC device 20 for operating upon numerical information commands externally inputted through a terminal 10, and a working machine 30 controlled using the values calculated in the NC device 20. The NC device 20 comprises an input section 21, an operation section 22 for processing commands from the input section 21, a memory section 23 for storing the results of processing in the operation section 22 or the instructions from the input section 21, a control section 24 for controlling the processing of the operation section 22, and an output section 25 for externally outputting processed values.
In the working machine 30, a tool 31 is attached to a tool holder 32 which is in turn attached to a chuck of a spindle 33. The spindle 33 is rotated by a spindle motor 34 which is driven by a signal from the output section 25 of the NC device 20. A workpiece 40 is fixed onto a table 35 of the working machine 30 by means of a jig or the like. In FIG. 1, reference numeral 36 designates a ball screw for moving the table 35 in the direction of the X-axis. The ball screw 36 is driven by an X-axis feed motor 38 through a gear box 37. The X-axis feed motor 38 is driven by a signal from the output section 25 of the NC device 20. Similarly to the arrangement for the X-axis, mechanisms (not shown) are provided for moving the table 35 in the Y-axis and Z-axis directions respectively, and are driven by a signal from the NC device 20.
An example will be described hereunder in which the NC working process as outlined above is applied to a lathe.
In FIG. 2, which is a schematic diagram of a lathe, a cylindrical work 2 is supported at one end by a forward end portion 3a of a tail 3 and is positioned and fixed in a chuck 1 rotated about a rotary axis (Z-axis). A tool 5 for cutting the work 2 is fixed onto a capstan rest 4. In cutting the work 2, the capstan rest 4 is moved in the direction Z, as indicated by an arrow, whereby the work 2 is cut.
In FIG. 3, the work 2 is illustrated by a solid line, the final shape 6 of the work 2 is shown by a two-dot chain line, and the cut portion 7 of the work 2 is shown by oblique lines.
In FIG. 4, the working path for obtaining the final shape 6 is shown and consists of working path elements l.sub.1, l.sub.2, l.sub.3, and l.sub.4. The tool 5 is caused to move along the working path in the order of the original point Q.sub.0 .fwdarw.a path m.sub.1 .fwdarw.a first working start point Q.sub.1 .fwdarw.working path element l.sub.1 .fwdarw.a second working start point Q.sub.2 .fwdarw.working path element l.sub.2 .fwdarw.a third working start point Q.sub.3 .fwdarw.working path element l.sub.3 .fwdarw.a fourth working start point Q.sub.4 .fwdarw.working path element l.sub.4 .fwdarw.a path m.sub.2 .fwdarw.the original point Q.sub.0, to thereby obtain the final worked shape 6.
In the conventional NC working process, there is a problem in that when a final shape for the work is inputted, the working path is determined regardless of the shape of the workpiece before machining, so that the amount of useless movement of the tool increases depending on the shape of the workpiece before machining, sometimes resulting in a very wasteful operation. This problem will be discussed hereunder referring to FIGS. 5 and 6.
In FIG. 5, by way of example, a piece 2 which has been cut in advance is shown, and in FIG. 6, the working path for obtaining a final shape 6 is illustrated. Thus, the same working path as that in FIG. 4 is set in accordance with the desired final shape even for a preworked workpiece. In FIG. 8, the working paths l.sub.1, l.sub.2, l.sub.3 and l.sub.4 are set without regard to the shape of the workpiece before machining, and therefore in this case the tool 5 is caused to move at a relatively slow speed along parts of the working path where the workpiece 2 does not exist, resulting in lost working time.